Conventionally, as an electric water pump which has the number of parts reduced, and is small and inexpensive, for example, there is known the electric water pump configured as follows. In the electric water pump, as shown in FIG. 3, a pump part 52 is formed at one end side of a main shaft 51 arranged within a housing 50, and a motor part 53 is formed at the other end side. The electric water pump is provided with a housing base 56 which partitions a motor housing 54 accommodating the motor part 53 therein and a pump housing 55 accommodating the pump part 52 therein. In the housing base 56, a through hole 56a for inserting the main shaft 51 therein is formed, and on the motor part 53 side of the main shaft 51, a large diameter part 51a supporting a magnet 58 is formed. A rotor part 57 of the motor is formed by these large diameter part 51a and magnet 58. The main shaft 51 is rotatably supported by a ball bearing 60 arranged on a bottom part 59 of the motor housing 54, and a bearing sleeve 61. The sleeve 61 constitutes a slide bearing which supports rotation of the main shaft 51 and is constituted as a stationary side seal ring of a mechanical seal for shaft-sealing the through hole 56a of the housing base 56, and is fitted to the inner periphery of the through hole 56a of the housing base 56 via an O-ring 62, and a convex part 61a provided on the end thereof is pressed to the large diameter part 51a constituting the rotor part 57 (Hereinafter, referred to as “Conventional Art”. For example, see Patent Citation 1.).